alamb opened a new issue #1931:
URL: https://github.com/apache/arrow-datafusion/issues/1931


   **Is your feature request related to a problem or challenge? Please describe 
what you are trying to do.**
   
   The `ListingFileProvider` after 
https://github.com/apache/arrow-datafusion/pull/1860 uses `UInt16` for the 
indexes of the `DictionaryArray` type
   
   This means that the number of partitions is limited to `2^16` ~ `64K`. It 
also means when scanning files from a source that have fewer than 256 distinct 
values (that could have fit in `UInt8`) there is wasted space and time using 
larger than needed dictionary columns (which will all have the same value).
   
   **Describe the solution you'd like**
   Ideally the partition column would be a constant (or a DictionaryArray with 
`UInt8` indexes) and the various upstream operations would create 
`DictionaryArrays` with larger index sizes as needed
   
   **Additional context**
   SUggested by @rdettai on 
https://github.com/apache/arrow-datafusion/pull/1860 at 
https://github.com/apache/arrow-datafusion/pull/1860#issuecomment-1056764995 
and https://github.com/apache/arrow-datafusion/pull/1860#issuecomment-1058110737
   


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